Floating data line circuit and method

ABSTRACT

A write line circuit includes a power supply node configured to carry a power supply voltage level, a reference node configured to carry a reference voltage level, an output node, first and second switching devices coupled in series between the output node and the power supply node, and a third switching device directly coupled to each of the output node and the reference node. The first switching device is configured to selectively couple the output node to the second switching device responsive to a first data signal, the second switching device is configured to selectively couple the first switching device to the power supply node responsive to a second data signal, and the third switching device is configured to selectively couple the output node to the reference node responsive to the first data signal.

PRIORITY CLAIM

The present application is a continuation of U.S. application Ser. No.16/204,268, filed Nov. 29, 2018, which claims the priority of U.S.Provisional Application No. 62/691,599, filed Jun. 28, 2018, each ofwhich is incorporated herein by reference in its entirety.

BACKGROUND

Memory arrays often include memory cells arranged in columnscorresponding to bit locations and rows corresponding to word locations.In such arrangements, during read and write operations, the memory cellsassociated with a given word are activated through one or more wordlines at a row location corresponding to the given word, and data aretransferred to and from the memory cells through one or more data linesat column locations corresponding to bits of the given word.

Input-output (IO) circuits used to transfer data in read and writeoperations are sometimes shared among multiple columns within segmentsof the array, each column being selectable through a switching circuit.In some cases, one or more bits of a word are masked by IO circuits sothat data are written to a subset of the memory cells associated withthe word during a write operation.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a diagram of a memory circuit, in accordance with someembodiments.

FIG. 2 is a diagram of a driving circuit, in accordance with someembodiments.

FIG. 3 is a diagram of a driving circuit, in accordance with someembodiments.

FIG. 4 is a diagram of a pre-charge circuit, in accordance with someembodiments.

FIG. 5 is a plot of memory circuit operating parameters, in accordancewith some embodiments.

FIG. 6 is a flowchart of a method of floating a data line, in accordancewith some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components, values, operations, materials,arrangements, or the like, are described below to simplify the presentdisclosure. These are, of course, merely examples and are not intendedto be limiting. Other components, values, operations, materials,arrangements, or the like, are contemplated. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

In various embodiments, a write line circuit of a memory circuitincludes power supply and reference nodes that carry power supply andreference voltage levels, first, second, and third input nodes thatreceive first and second data signals and a control signal, and anoutput node. Responsive to the first and second data signals and thecontrol signal, the write line circuit either outputs one of the powersupply or reference voltage levels on the output node, or floats theoutput node.

The write line circuit is thereby capable of driving a data line tologically high and low states during write operations, floating the dataline during masked write operations and, in some embodiments,pre-charging the data line to the logically high state between writeoperations. Compared to approaches that do not enable floating a dataline during a masked write operation, the write line circuit reducescurrent flow in a selected memory cell and associated bit and datalines, thereby improving circuit reliability and energy efficiency. Bypre-charging the data line between write operations, the write linecircuit prevents the data line from discharging toward the referencevoltage level, thereby avoiding possible increases in current flow andwrite times.

FIG. 1 is a diagram of a memory circuit 100, in accordance with someembodiments. Memory circuit 100 includes segments 110U and 110D, eachelectrically coupled with a write line WLB and a write line WLT. A writeline circuit 120B is electrically coupled with write line WLB, and awrite line circuit 120T is electrically coupled with write line WLT.

Two or more circuit elements are considered to be electrically coupledbased on a direct electrical connection or an electrical connection thatincludes one or more additional circuit elements and is thereby capableof being controlled, e.g., made resistive or open by a transistor orother switching device.

Memory circuit 100 is a subset of a memory macro (not shown) thatincludes one or more additional components, e.g., at least one segment(not shown) in addition to segments 110U and 110D and/or at least onewrite line circuit (not shown) in addition to write line circuits 120Band 120T. In various embodiments, memory circuit does not include one ormore of segment 110U, segment 110D, write line circuit 120B, write linecircuit 120T, write line WLB, or write line WLT.

Each of segments 110U and 110D is a segment of a memory array of thememory macro and includes a selection circuit 112 electrically coupledwith a plurality of N complementary bit line pairs BL[0 . . . N]/BLB[0 .. . N]. Each bit line pair BL[n]/BLB[n] is electrically coupled with abit line pre-charger 114 and with a plurality of memory cells 116. Invarious embodiments, at least one of segments 100U or 110D includes aplurality of individual bit lines, e.g., either BL[0 . . . N] or BLB[0 .. . N], instead of plurality of bit line pairs BL[0 . . . N]/BLB[0 . . .N].

Write lines WLB and WLT and bit line pairs BL[0 . . . N]/BLB[0 . . . N]of segments 110U and 110D are data lines including conductive elementscapable of transferring voltage levels to and/or from plurality ofmemory cells 116.

In some embodiments, each of segments 110U and 110D includes four bitline pairs. In various embodiments, one or both of segments 110U or 110Dincludes fewer or greater than four bit line pairs.

In the embodiment depicted in FIG. 1 , segment 110U is oriented in anupward direction relative to write line circuits 120B and 120T, andsegment 110D is oriented in a downward direction relative to write linecircuits 120B and 120T. In various embodiments, segments 110U and 110Dhave orientations other than those depicted in FIG. 1 .

Selection circuit 112 is configured to selectively couple write line WLTwith a bit line BL[n] and write line WLB with a bit line BLB[n]responsive to a selection signal (not shown) having a statecorresponding to selection of bit line pair BL[n]/BLB[n]. In someembodiments, selection circuit 112 includes a multiplexer.

Bit line pre-charger 114 includes a circuit configured to charge a givenbit line pair to a power supply voltage level responsive to a pre-chargeenable signal. Segment 110U is configured so that bit line pre-charger114 receives a pre-charge enable signal BLEQB_UP on an enable line (notlabeled), and segment 110D is configured so that bit line pre-charger114 receives a pre-charge enable signal BLEQB_DN on an enable line (notlabeled).

Each plurality of memory cells 116 is arranged as a column of the memoryarray. In various embodiments, a column of memory cells 116 includes anumber of memory cells 116 ranging from 128 to 1024, fewer than 128, orgreater than 1024.

A given plurality of memory cells 116 includes electrical,electromechanical, electromagnetic, or other devices (not individuallylabeled) configured to store bit data represented by logical states. Thelogical states of a memory cell 116 are capable of being programmed in awrite operation and detected in a read operation.

In some embodiments, a logical state corresponds to a voltage level ofan electrical charge stored in a given memory cell. In some embodiments,a logically high state corresponds to a power supply voltage level ofmemory circuit 100 and a logically low state corresponds to a referencevoltage level of memory circuit 100. In some embodiments, a logicalstate corresponds to a physical property, e.g., a resistance or magneticorientation, of a component of a given memory cell.

In some embodiments, plurality of memory cells 116 includes staticrandom-access memory (SRAM) cells. In various embodiments, SRAM cellsinclude five-transistor (5T) SRAM cells, six-transistor (6T) SRAM cells,eight-transistor (8T) SRAM cells, nine-transistor (9T) SRAM cells, orSRAM cells having other numbers of transistors. In some embodiments,plurality of memory cells 116 includes dynamic random-access memory(DRAM) cells or other memory cell types capable of storing bit data.

A plurality of word lines, represented in FIG. 1 by an example word lineWL[x], intersects bit line pairs BL[0 . . . N]/BLB[0 . . . N]. Memorycircuit 100 is thereby configured so that a given word line, e.g., wordline WL[x], is communicatively coupled with one memory cell 116 in eachcolumn of memory cells 116 of a given one of segments 110U or 110D.

Two or more circuit elements are considered to be communicativelycoupled based on a direct signal connection or on an indirect signalconnection that includes one or more logic devices, e.g., an inverter orlogic gate, between the two or more circuit elements. In someembodiments, signal communications between the two or morecommunicatively coupled circuit elements are capable of being modified,e.g., inverted or made conditional, by the one or more logic devices.

In operation, a memory cell 116 at a location corresponding to bit linepair BL[n]/BLB[n] and word line WL[x] is electrically coupled with oneor both of write line WLT or WLB through bit line pair BL[n]/BLB[n]responsive to a word line signal (not labeled) on word line WL[x], andthrough the corresponding selection circuit 112 responsive to theselection signal having the state corresponding to selection of bit linepair BL[n]/BLB[n].

Each of write line circuits 120B and 120T includes a driving circuit 122and a pre-charge circuit 124. Driving circuit 122 is electricallycoupled between a power supply node VDD, configured to carry the powersupply voltage level of memory circuit 100, a reference node VSS,configured to carry the reference voltage level of memory circuit 100,and an output node OUT. Pre-charge circuit 124 is electrically coupledbetween power supply node VDD and output node OUT.

In various embodiments, memory circuit 100 is part of a larger system,e.g., a system on a chip, and the power supply voltage level of memorycircuit 100 corresponds to an operational voltage level of the system orto a memory-specific operational voltage level. In various embodiments,memory circuit 100 is part of a larger system, and the reference voltagelevel of memory circuit 100 corresponds to a reference voltage level ofthe system or to a memory-specific reference voltage level. In someembodiments, reference node VSS is a ground voltage node having a groundvoltage level.

Driving circuit 122 is communicatively coupled with input nodes D1 andD2 and electrically coupled with output node OUT, and pre-charge circuit124 is communicatively coupled with input nodes C1 and C2.

In the embodiment depicted in FIG. 1 , write line circuit 120B isconfigured to receive a data signal GDT at input node D1, a data signalGDB at input node D2, pre-charge enable signal BLEQB_DN at input nodeC1, and pre-charge enable signal BLEQB_UP at input node C2, and tooutput a write line signal WB at output node OUT electrically coupledwith write line WLB.

In the embodiment depicted in FIG. 1 , write line circuit 120T isconfigured to receive data signal GDB at input node D1, data signal GDTat input node D2, pre-charge enable signal BLEQB_DN at input node C1,and pre-charge enable signal BLEQB_UP at input node C2, and to output awrite line signal WT at output node OUT electrically coupled with writeline WLT.

A given driving circuit 122 is configured to, responsive to logicalstates of data signals received at input nodes D1 and D2, either outputone of the power supply voltage level or the reference voltage level atoutput node OUT or float output node OUT by having a high outputimpedance at output node OUT.

Driving circuit 122 is configured to output the write line signal havingone of the power supply voltage level or the reference voltage level atoutput node OUT responsive to the logical state of the data signalreceived at input node D1. In various embodiments, driving circuit 122is configured to output the write line signal having the power supplyvoltage level responsive to one of a low or a high logical state atinput node D1, and to output the write line signal having the referencevoltage level responsive to the other of the low or the high logicalstate at input node D1.

In some embodiments, driving circuit 122 includes an inverter, e.g.,transistors N1 and P1 discussed below with respect to FIGS. 2 and 3 ,and is thereby configured to output the write line signal having thepower supply voltage level responsive to the low logical state at inputnode D1, and to output the write line signal having the referencevoltage level responsive to the high logical state at input node D1.

In the embodiment depicted in FIG. 1 , write line circuit 120B includesdriving circuit 122 configured to receive data signal GDT at input nodeD1, and is thereby configured to output write line signal WB having oneof the power supply voltage level or the reference voltage level towrite line WLB responsive to the logical state of data signal GDT.

In the embodiment depicted in FIG. 1 , write line circuit 120T includesdriving circuit 122 configured to receive data signal GDB at input nodeD1, and is thereby configured to output write line signal WT having oneof the power supply voltage level or the reference voltage level towrite line WLT responsive to the logical state of data signal GDB.

Driving circuit 122 is configured to either float output node OUT oroutput the write line signal having one of the power supply voltagelevel or the reference voltage level responsive to the logical states ofthe data signals received on input nodes D1 and D2. In variousembodiments, driving circuit 122 is configured to float output node OUTresponsive to one or more combinations of a low or high logical state atinput node D1 and a low or high logical state at input node D2, and tooutput the write line signal having one of the power supply voltagelevel or the reference voltage level responsive to one or more othercombinations of the low or high logical state at input node D1 and thelow or high logical state at input node D2.

In the embodiment depicted in FIG. 1 , driving circuit 122 is configuredto, in operation, float output node OUT in response to the low logicalstate at each of input nodes D1 and D2, output the write line signalhaving the power supply voltage level in response to the low logicalstate at input node D1 and the high logical state at input node D2, andoutput the write line signal having the reference voltage level inresponse to the high logical state at input node D1 and either the lowor the high logical state at input node D2.

In various embodiments, driving circuit 122 is configured to have thehigh output impedance at output node OUT by including one or moreswitching devices (not depicted in FIG. 1 ) electrically coupled withoutput node OUT. A switching device includes one or more electrical orelectro-mechanical constructions capable of making and breakingelectrical connections between two or more terminals responsive tovoltage levels representing logical states received at one or morecontrol terminals. In various embodiments, a switching device includesone or more of a transistor, transmission gate, or other device suitablefor controlling electrical connections.

In various embodiments, a transistor includes one or a combination of afield-effect transistor (FET), a metal-oxide-semiconductor field-effecttransistor (MOSFET), a fin field-effect transistor (FinFET), an n-typetransistor, a p-type transistor, a vertical gate transistor, a bipolaror other transistor type.

In some embodiments, driving circuit 122 includes one or more switchingdevices, e.g., a transistor P2 discussed below with respect to FIG. 2 ,configured to selectively decouple driving circuit 122 from power supplynode VDD responsive to the data signal received at input node D2, and isthereby at least partially capable of having the high output impedanceat output node OUT.

In some embodiments, driving circuit 122 includes one or more switchingdevices, e.g., transistor N1 discussed below with respect to FIGS. 2 and3 , configured to selectively decouple driving circuit 122 fromreference node VSS responsive to the data signal received at input nodeD1, and is thereby at least partially capable of having the high outputimpedance at output node OUT.

In some embodiments, driving circuit 122 includes one or more switchingdevices, e.g., a transistor P3 discussed below with respect to FIG. 3 ,configured to selectively decouple driving circuit 122 from output nodeOUT responsive to the data signals received at input nodes D1 and D2,and is thereby at least partially capable of having the high outputimpedance at output node OUT.

In various embodiments, driving circuit 122 includes one or more logicgates, e.g., a NOR gate NOR1 discussed below with respect to FIG. 3 ,configured to receive the data signals at one or both of input nodes D1or D2 and generate one or more switching signals capable of controllingone or more switching devices, driving circuit 122 thereby beingconfigured to be at least partially capable of having the high outputimpedance at output node OUT. In various embodiments, driving circuit122 includes one or more of an inverter, OR gate, NOR gate, XOR gate,AND gate, NAND gate, or other logic gate suitable for applying a logicscheme.

In the embodiment depicted in FIG. 1 , write line circuit 120B includesdriving circuit 122 configured to receive data signals GDT and GDB atrespective input nodes D1 and D2, and is thereby configured to eitherfloat write line WLB or output write line signal WB having one of thepower supply voltage level or the reference voltage level to write lineWLB responsive to the logical states of data signals GDT and GDB.

In the embodiment depicted in FIG. 1 , write line circuit 120T includesdriving circuit 122 configured to receive data signals GDB and GDT atrespective input nodes D1 and D2, and is thereby configured to eitherfloat write line WLT or output write line signal WT having one of thepower supply voltage level or the reference voltage level to write lineWLT responsive to the logical states of data signals GDB and GDT.

A given pre-charge circuit 124 is configured to, responsive to logicalstates of enable signals received at input nodes C1 and C2, eitheroutput the power supply voltage level at output node OUT or float outputnode OUT by having a high output impedance at output node OUT. Inoperation, a pre-charge circuit 124 floating the associated output nodeOUT allows the associated driving circuit 122 to control output nodeOUT, and a given driving circuit 122 floating the associated output nodeOUT allows the associated pre-charge circuit 124 to control output nodeOUT.

By including driving circuit 122 and pre-charge circuit 124 as depictedin FIG. 1 , write line circuits 120B and 120T are configured to eitheroutput the write line signal having one of the power supply voltagelevel or the reference voltage level at output node OUT, or float outputnode OUT responsive to a combination of the data signals received atinput nodes D1 and D2 and the enable signals received at input nodes C1and C2.

In various embodiments, pre-charge circuit 124 is configured to outputthe power supply voltage level responsive to one or more combinations ofa low or high logical state at input node C1 and a low or high logicalstate at input node C2, and to float output node OUT responsive to oneor more other combinations of the low or high logical state at inputnode C1 and the low or high logical state at input node C2.

In some embodiments, one or both of write line circuits 120B and 120Tdoes not include one of input nodes C1 or C2, and pre-charge circuit 124is configured to either output the power supply voltage level at outputnode OUT or float output node OUT responsive to a low or high logicalstate at a single input node C1 or C2. In some embodiments, one or bothof write line circuits 120B and 120T includes one or more input nodes(not shown) in addition to input nodes C1 and C2, and pre-charge circuit124 is configured to either output the power supply voltage level atoutput node OUT or float output node OUT responsive to combinations ofthe low or high logical states at some or all of the input nodes.

In some embodiments, one or both of write line circuits 120B or 120Tdoes not include pre-charge circuit 124, and the one or both of writeline circuits 120B or 120T is configured to either output the write linesignal having one of the power supply voltage level or the referencevoltage level at output node OUT or float output node OUT responsivesolely to the data signals received at input nodes D1 and D2.

In some embodiments, pre-charge circuit 124 includes a switching device,e.g., a transistor P4 discussed below with respect to FIG. 4 ,configured to selectively decouple output node OUT from power supplynode VDD responsive to the enable signal received at input node C1, andis thereby at least partially capable of having the high outputimpedance at output node OUT.

In some embodiments, pre-charge circuit 124 includes a switching device,e.g., a transistor P5 discussed below with respect to FIG. 4 ,configured to selectively decouple output node OUT from power supplynode VDD responsive to the enable signal received at input node C2, andis thereby at least partially capable of having the high outputimpedance at output node OUT.

In some embodiments, pre-charge circuit 124 includes a single switchingdevice, e.g., one of transistors P4 or P5 discussed below with respectto FIG. 4 , configured to selectively decouple output node OUT frompower supply node VDD responsive to the enable signals received at bothof input nodes C1 and C2, and is thereby at least partially capable ofhaving the high output impedance at output node OUT. In someembodiments, pre-charge circuit 124 includes one or more logic circuits(not shown) configured to control a switching device responsive to theenable signals received at both of input nodes C1 and C2.

In the embodiment depicted in FIG. 1 , each of write line circuits 120Band 120T includes pre-charge circuit 124 configured to receive enablesignal BLEQB_DN at input node C1 and enable signal BLEQB_UP at inputnode C2. Write line circuit 120B is thereby configured to either outputthe power supply voltage level to write line WLB or float write line WLBresponsive to the logical states of enable signals BLEQB_DN andBLEQB_UP, and write line circuit 120T is thereby configured to eitheroutput the power supply voltage level to write line WLT or float writeline WLT responsive to the logical states of enable signals BLEQB_DN andBLEQB_UP.

Memory circuit 100 is configured so that, between write operations,enable signals BLEQB_DN and BLEQB_UP are received at respective inputnodes C1 and C2 having logical states that cause pre-charge circuit 124to output the power supply voltage level to output node OUT, and, duringwrite operations, enable signals BLEQB_DN and BLEQB_UP are received atrespective input nodes C1 and C2 having logical states that causepre-charge circuit 124 to float output node OUT.

Between write operations, pre-charge circuit 124 outputting the powersupply voltage level to output node OUT enables write line circuit 120Bto maintain write line WLB at the power supply voltage level, andenables write line circuit 120T to maintain write line WLT at the powersupply voltage level. During write operations, pre-charge circuit 124floating output node OUT enables write line WLB to be controlled bydriving circuit 122 of write line circuit 120B, and enables write lineWLT to be controlled by driving circuit 122 of write line circuit 120T.

During a write operation in which a data bit is being written to amemory cell 116 in a selected bit line pair BL[n]/BLB[n] of either ofsegments 110U or 110D, memory circuit 100 is configured so that datasignals GDT and GDB are received as a complementary pair. During thewrite operation in which data signals GDT and GDB are received as acomplementary pair, based on the configuration discussed above, writeline circuit 120B outputs write line signal WB having one of the powersupply voltage level or the reference voltage level to write line WLB,and write line circuit 120T outputs write line signal WT having theother of the power supply voltage level or the reference voltage levelto write line WLT.

During a write operation in which a data bit corresponding to a memorycell 116 in a selected bit line pair BL[n]/BLB[n] of either of segments110U or 110D is masked, memory circuit 100 is configured so that each ofdata signals GDT and GDB is received having the low logical state.During the write operation in which data signals GDT and GDB arereceived having the low logical state, based on the configurationdiscussed above, write line circuit 120B floats write line WLB, andwrite line circuit 120T floats write line WLT.

In some embodiments, during a write operation in which a data bitcorresponding to a memory cell 116 in a selected bit line pairBL[n]/BLB[n] of either of segments 110U or 110D is masked, memorycircuit 100 is configured so that each of data signals GDT and GDB isreceived having the high logical state, and, based on the configurationdiscussed above, write line circuit 120B floats write line WLB, andwrite line circuit 120T floats write line WLT.

As discussed above, memory circuit 100 is configured so that, during awrite operation, in some embodiments, a selected memory cell 116 iselectrically coupled with the corresponding bit line pair BL[n]/BLB[n]in response to the word line signal on the corresponding word lineWL[x], and the bit line pair BL[n]/BLB[n] is electrically coupled withrespective write lines WLT and WLB through selection circuit 112.

In the case in which the data bit is not masked in the write operation,write line circuits 120B and 120T outputting respective write linesignals WB and WT having the power supply and reference voltage levelsas a complementary pair cause the data bit to be written to the selectedmemory cell 116.

In the case in which the data bit is masked in the write operation,write line circuits 120B and 120T floating respective write lines WLBand WLT cause the selected memory cell 116 to be electrically coupledwith floating respective bit lines BLB [n] and BL[n].

Compared to approaches in which a selected memory cell is electricallycoupled with bit lines that are not floating during a write operation inwhich a data bit is masked, e.g., approaches in which bit lines are heldat or near a power supply voltage level during a write operation inwhich a data bit is masked, the configuration of memory circuit 100reduces current flow in the selected cell and associated bit lines andwrite lines, thereby improving circuit reliability and energyefficiency.

The benefits discussed above are further achieved by memory circuit 100being configured to maintain write lines WLB and WLT at the power supplyvoltage level between write operations, thereby preventing one or bothof write lines WLB or WLT from discharging through leakage currents to avoltage level at or near the reference voltage level, in which case amemory cell could be unintentionally programmed during a masked writeoperation.

FIG. 2 is a diagram of a driving circuit 200, in accordance with someembodiments. Driving circuit 200 is usable as a driving circuit 122discussed above with respect to FIG. 1 . Driving circuit 200 includesPMOS transistors P1 and P2 and NMOS transistor N1 electrically coupledin series between power supply node VDD and reference node VSS.

Transistors N1 and P1 are configured as an inverter, also referred to asa write driver 210, in which a source of transistor N1 is electricallycoupled with reference node VSS, a drain of transistor N1 iselectrically coupled with a drain of transistor P1, and a gate oftransistor N1 is communicatively coupled with a gate of transistor P1. Asource of transistor P1 is electrically coupled with a drain oftransistor P2, and a source of transistor P2 is electrically coupledwith power supply node VDD.

The gates of transistors N1 and P1 are communicatively coupled withinput node D1, and the drains of transistors N1 and P1 are electricallycoupled with output node OUT. An inverter INV1 is coupled between inputnode D2 and a gate of transistor P2, with an input terminal (notlabeled) communicatively coupled with input node D1, and an outputterminal (not labeled) communicatively coupled with the gate oftransistor P2.

In operation, the low logical state at input node D1 is received at thegates of transistors N1 and P1, thereby turning off transistor N1 anddecoupling output node OUT from reference node VSS, and turning ontransistor P1 and electrically coupling output node OUT with the drainof transistor P2. The high logical state at input node D1 is received atthe gates of transistors N1 and P1, thereby turning on transistor N1 andelectrically coupling output node OUT with reference node VSS, andturning off transistor P1 and decoupling output node OUT from the drainof transistor P2.

In operation, the low logical state at input node D2 is inverted byinverter INV1 to the high logical state at the gate of transistor P2,thereby turning off transistor P2 and decoupling the source oftransistor P1 from power supply node VDD. The high logical state atinput node D2 is inverted by inverter INV1 to the low logical state atthe gate of transistor P2, thereby turning on transistor P2 andelectrically coupling the source of transistor P1 with power supply nodeVDD.

Inverter INV1 and transistor P2 are also referred to as an interruptcircuit 220. In some embodiments, driving circuit 200 includes aninterrupt circuit 220 that does not include inverter INV1, and in whichtransistor P2 is an NMOS transistor. In these embodiments, in operation,the low logical state at input node D2 turns off transistor P2, and thehigh logical state at input node D2 turns on transistor P2.

In operation, the low logical state at input nodes D1 and D2, by turningoff transistors N1 and P2, decouples output node OUT from both referencenode VSS and power supply node VDD, thereby floating output node OUT byhaving a high impedance at output node OUT.

In operation, the low logical state at input node D1 and the highlogical state at input node D2, by turning off transistor N1 and turningon transistors P1 and P2, decouples output node OUT from reference nodeVSS and electrically couples output node OUT with power supply node VDD,thereby outputting the power supply voltage level on output node OUT.

In operation, the high logical state at input node D1 and the lowlogical state at input node D2, by turning on transistor N1, and turningoff transistors P1 and P2, electrically couples output node OUT withreference node VSS and decouples output node OUT from power supply nodeVDD, thereby outputting the reference voltage level on output node OUT.

In operation, the high logical state at input node D1 and the highlogical state at input node D2, by turning on transistors N1 and P2, andturning off transistor P1, electrically couples output node OUT withreference node VSS and decouples output node OUT from power supply nodeVDD, thereby outputting the reference voltage level on output node OUT.

By the configuration discussed above, driving circuit 200 is capable ofenabling the benefits discussed above with respect to memory circuit 100and FIG. 1 .

FIG. 3 is a diagram of a driving circuit 300, in accordance with someembodiments. Driving circuit 300 is usable as a driving circuit 122discussed above with respect to FIG. 1 .

Driving circuit 300 includes write driver 210, which includestransistors N1 and P1, discussed above with respect to FIG. 2 , but doesnot include inverter INV1 or transistor P2 of interrupt circuit 220. Inaddition to write driver 210, driving circuit 300 includes a node INT,NOR gate NOR1, and PMOS transistor P3.

Write driver 210 includes transistors N1 and P1 electrically coupled inseries between power supply node VDD and reference node VSS, with thesource of transistor N1 electrically coupled with reference node VSS,and the source of transistor P1 electrically coupled with power supplynode VDD.

The drains of transistors N1 and P1 are electrically coupled with nodeINT, and transistor P3 is coupled between node INT and output node OUT.One of a source or drain of transistor P3 is electrically coupled withnode INT, and the other of the source or drain of transistor P3 iselectrically coupled with output node OUT. A gate of transistor P3 iscommunicatively coupled with an output terminal (not labeled) of NORgate NOR1.

In addition to the output terminal, NOR gate NOR1 includes two inputterminals (not labeled). A first input terminal is communicativelycoupled with input node D1, and a second input terminal iscommunicatively coupled with input node D2.

In operation, the low logical state at input node D1 is received at thegates of transistors N1 and P1, thereby turning off transistor N1 anddecoupling node INT from reference node VSS, and turning on transistorP1 and electrically coupling node INT with power supply node VDD.Conversely, the high logical state at input node D1 is received at thegates of transistors N1 and P1, thereby turning on transistor N1 andelectrically coupling node INT with reference node VSS, and turning offtransistor P1 and decoupling node INT from power supply node VDD.

In operation, the logical state received at input node D1 is received atthe first input terminal of NOR gate NOR1, and the logical statereceived at input node D2 is received at the second input terminal ofNOR gate NOR1.

In operation, the high logical state at input node D2 received at thesecond input of NOR gate NOR1 causes the output terminal of NOR gateNOR1, and thereby the gate of transistor P3, to have the low logicalstate for each of the low and high logical states at input node D1. Inresponse to the low logical state at the gate of transistor P3,transistor P3 is turned on, thereby electrically coupling node INT withoutput node OUT.

In operation, the low logical state at input node D2 received at thesecond input terminal of NOR gate NOR1 causes the output terminal of NORgate NOR1, and thereby the gate of transistor P3, to have a logicalstate based on the logical state at input node D1.

In this case, the low logical state at input node D1 received at thefirst input terminal of NOR gate NOR1 causes the output terminal of NORgate NOR1, and thereby the gate of transistor P3, to have the highlogical state, thereby turning off transistor P3 and decoupling node INTfrom output node OUT. The high logical state at input node D1 receivedat the first input terminal of NOR gate NOR1 causes the output terminalof NOR gate NOR1, and thereby the gate of transistor P3, to have the lowlogical state, thereby turning on transistor P3 and electricallycoupling node INT with output node OUT.

In operation, the low logical state at input nodes D1 and D2, by turningoff transistors N1 and P3, decouples output node OUT from node INT andtherefore both reference node VSS and power supply node VDD, therebyfloating output node OUT by having a high impedance at output node OUT.

In operation, the low logical state at input node D1 and the highlogical state at input node D2, by turning off transistor N1 and turningon transistors P1 and P3, decouples output node OUT from reference nodeVSS and electrically couples output node OUT with power supply node VDDvia node INT, thereby outputting the power supply voltage level onoutput node OUT.

In operation, the high logical state at input node D1 and the lowlogical state at input node D2, by turning on transistors N1 and P3, andturning off transistor P1, electrically couples output node OUT withreference node VSS via node INT, and decouples output node OUT frompower supply node VDD, thereby outputting the reference voltage level onoutput node OUT.

In operation, the high logical state at input node D1 and the highlogical state at input node D2, by turning on transistors N1 and P3, andturning off transistor P1, electrically couples output node OUT withreference node VSS via node INT, and decouples output node OUT frompower supply node VDD, thereby outputting the reference voltage level onoutput node OUT.

By the configuration discussed above, driving circuit 300 is capable ofenabling the benefits discussed above with respect to memory circuit 100and FIG. 1 .

FIG. 4 is a diagram of a pre-charge circuit 400, in accordance with someembodiments. Pre-charge circuit 400 is usable as a pre-charge circuit124 discussed above with respect to FIG. 1 .

Pre-charge circuit 400 includes PMOS transistors P4 and P5 electricallycoupled in series between power supply node VDD and output node OUT. Adrain of transistor P4 is electrically coupled with output node OUT, asource of transistor P4 is electrically coupled with a drain oftransistor P5, and a source of transistor P5 is electrically coupledwith power supply node VDD. A gate of transistor P4 is communicativelycoupled with input node C1, and a gate of transistor P5 iscommunicatively coupled with input node C2.

In operation, the low logical state at input node C1 is received at thegate of transistor P4, thereby causing transistor P4 to turn on,electrically coupling output node OUT with the drain of transistor P5.The high logical state at input node C1 is received at the gate oftransistor P4, thereby causing transistor P4 to turn off, electricallydecoupling output node OUT from the drain of transistor P5, and therebyfrom power supply node VDD.

In operation, the low logical state at input node C2 is received at thegate of transistor P5, thereby causing transistor P5 to turn on,electrically coupling the source of transistor P4 with power supply nodeVDD. The high logical state at input node C2 is received at the gate oftransistor P5, thereby causing transistor P5 to turn off, electricallydecoupling the source of transistor P4, and thereby output node OUT,from power supply node VDD.

Pre-charge circuit 400 is thereby configured so that, in operation, thehigh logical state at either of input nodes C1 or C2 causes output nodeOUT to be decoupled from power supply node VDD, and the low logicalstate at both of input nodes C1 and C2 causes output node OUT to beelectrically coupled with power supply node VDD.

By the configuration discussed above, pre-charge circuit 400 is capableof enabling the benefits discussed above with respect to memory circuit100 and FIG. 1 .

FIG. 5 is a plot of memory circuit operating parameters, in accordancewith some embodiments. FIG. 5 depicts non-limiting examples of datasignals GDT and GDB, enable signals BLEQB_UP and BLEQB_DN, write linesignals WB and WT, each discussed above with respect to FIG. 1 , and twobit line voltages BL and BLB. Bit line voltages BL and BLB representnon-limiting examples of voltage levels on one pair of bit line pairsBL[n]/BLB[n] discussed above with respect to FIG. 1 .

An interval from a time t1 to a time t2 represents a first writeoperation in which a data bit is written to a selected memory cell 116in segment 110U corresponding to the bit line pair BL[n]/BLB[n]. Aninterval from a time t3 to a time t4 represents a second write operationin which the selected memory cell 116 is masked. Timing and control ofthe various signals during the write operations are based on one or moresignals, e.g., a clock signal or a mask enable signal, that are notdepicted for the purpose of clarity.

Prior to time t1, each of data signals GDT and GDB is at the low logicalstate. At time t1, the start of the first write operation, data signalGDT transitions from the logically low state to the logically highstate, and data signal GDB remains at the low logical state, thediffering logical states representing the data bit. In a complementarywrite operation (not depicted), a complementary data bit is representedby data signal GDB transitioning from the logically low state to thelogically high state, and data signal GDT remaining at the low logicalstate.

At time t2, the end of the first write operation, data signal GDTtransitions from the logically high state back to the logically lowstate, and data signal GDB remains at the logically low state.

From time t3 to time t4, each of data signals GDT and GDB remains at thelogically low state, corresponding to the selected memory cell 116 beingmasked in the second write operation.

From time t1 to time t2, enable signal BLEQB_UP toggles from thelogically low state to the logically high state, and back to thelogically low state, corresponding to the memory cell 116 in segment110U being selected in the first write operation. Enable signal BLEQB_DNremains at the logically low state because a memory cell 116 in segment110D is not selected in the first write operation.

From time t3 to time t4, enable signal BLEQB_UP toggles from thelogically low state to the logically high state, and back to thelogically low state, corresponding to the memory cell 116 in segment110U being selected in the second write operation while enable signalBLEQB_DN remains at the logically low state because a memory cell 116 insegment 110D is not selected in the second write operation.

In the non-limiting example depicted in FIG. 5 , an enable signalBLEQB_UP or BLEQB_DN having the logically low state corresponds to agiven bit line pre-charger 114 being activated to charge a correspondingbit line pair BL[n]/BLB[n] to the power supply voltage level. An enablesignal BLEQB_UP or BLEQB_DN having the logically high state correspondsto the bit line pre-charger 114 being deactivated.

The bit line pre-charger 114 corresponding to the selected memory cell116 is therefore deactivated during both the first and second writeoperations based on enable signal BLEQB_UP toggling to the logicallyhigh state, and otherwise activated to charge the bit line pairBL[n]/BLB[n] corresponding to the selected memory cell 116 to the powersupply voltage level. Each of bit line voltages BL and BLB is therebycharged to the high logical state before time t1, from time t2 to timet3, and after time t4.

In the non-limiting example depicted in FIG. 5 , both of enable signalsBLEQB_UP and BLEQB_DN having the logically low state corresponds to agiven pre-charge circuit 124 outputting the power supply voltage levelto a corresponding output node. One or both of enable signals BLEQB_UPor BLEQB_DN having the logically high state corresponds to the givenpre-charge circuit 124 floating the corresponding output node.

Pre-charge circuits 124 of write line circuits 120T and 120B thereforefloat respective write lines WLT and WLB during the first and secondwrite operations, and output the power supply voltage level torespective write lines WLT and WLB before time t1, from time t2 to timet3, and after time t4.

During both the first and second write operations, based on theselection of the memory cell 116, bit line pair BL[n]/BLB[n] iselectrically coupled with respective write lines WLT and WLB. Becausethe bit line pre-charger 114 corresponding to the selected memory cell116 is deactivated, and write line circuits 120T and 120B floatrespective write lines WLT and WLB, write line signals WT and WBcorrespond to respective bit line voltages BL and BLB during the firstand second write operations.

During the first write operation, from time t1 to time t2, write linesignal WB and bit line voltage BLB toggle from the logically high stateto the logically low state and back to the logically high state,corresponding to driving circuit 122 of write line circuit 120Boutputting the reference voltage level to write line WLB in response toreceiving the high logical state of data signal GDT and the low logicalstate of data signal GDB.

During the first write operation, from time t1 to time t2, write linesignal WT and bit line voltage BL remain at the logically high state,corresponding to driving circuit 122 of write line circuit 120Toutputting the power supply voltage level to write line WLT in responseto receiving the low logical state of data signal GDB and the highlogical state of data signal GDT.

During the second write operation, from time t3 to time t4, because thebit line pre-charger 114 corresponding to the selected memory cell 116is deactivated, and each of write lines WLT and WLB is floating withrespect to write line circuits 120T and 120B, write line signals WT andWB and bit line voltages BL and BLB are controlled by the logical statesstored in the selected memory cell 116 during the first write operation.

Because write line signal WT and bit line voltage BL store the logicallyhigh state in the selected memory cell 116 during the first writeoperation, the selected memory cell 116 causes write line signal WT andbit line voltage BL to remain at the logically high state during thesecond write operation.

Because write line signal WB and bit line voltage BLB cause thelogically low state to be stored in the selected memory cell 116 duringthe first write operation, the selected memory cell 116 causes writeline signal WB and bit line voltage BLB to move toward the logically lowstate during the second write operation. The selected memory cellcausing the write line signal WB and bit line voltage BLB to move towardthe logically low state is also referred to as a dummy read operation.

The rates at which each of write line signal WB and bit line voltage BLBmove toward the logically low state is based on a current drivingcapacity of the selected memory cell 116 and distributed parasiticresistance and capacitance values of write line WLB and the bit line BLBand selection circuit 112 corresponding to the selected memory cell 116.

In the embodiment depicted in FIG. 5 , because bit line BLB[n] isbetween the corresponding selected memory cell 116 and write line WLB,the distributed parasitic resistance and capacitance values cause theselected memory cell 116 to move bit line voltage BLB faster than writeline WLB toward the logically low state.

FIG. 6 is a flowchart of a method 600 of floating a data line, inaccordance with one or more embodiments. Method 600 is usable with amemory circuit, e.g., memory circuit 100 discussed above with respect toFIG. 1 .

The sequence in which the operations of method 600 are depicted in FIG.6 is for illustration only; the operations of method 600 are capable ofbeing executed in sequences that differ from that depicted in FIG. 6 .In some embodiments, operations in addition to those depicted in FIG. 6are performed before, between, during, and/or after the operationsdepicted in FIG. 6 . In some embodiments, the operations of method 600are a subset of operations of a method of operating a memory circuit.

At operation 610, in some embodiments, a data line is coupled with apower supply node using a pre-charging circuit. The power supply nodecarries a power supply voltage level, and coupling the data line withthe power supply node causes the data line to have the power supplyvoltage level.

In some embodiments, at least one of the power supply node is one powersupply node of a plurality of power supply nodes, the data line is onedata line of a plurality of data lines, or the pre-charging circuit isone pre-charging circuit of a plurality of pre-charging circuits, andcoupling the data line with the power supply node includes at least oneof coupling more than one data line of the plurality of data lines,coupling with more than one power supply node of the plurality of powersupply nodes, or using more than one pre-charging circuit of theplurality of pre-charging circuits.

The pre-charging circuit couples the data line with the power supplynode in response to one or more logical states of a control signal orplurality of control signals. In various embodiments, at least one ofthe control signal or the plurality of control signals is an enablesignal, and a bit line pre-charger of the memory circuit responds to theenable signal by pre-charging a bit line pair associated with thepre-charging circuit. In some embodiments, a control signal is a signalthat is separate from an enable signal and based on one or more enablesignals.

In some embodiments, the one or more control signals change logicalstates in response to the end of a write operation on one or more memorycells associated with the pre-charging circuit. In some embodiments, thewrite operation includes writing data bits to each of one or more memorycells and masking the writing of data bits to each of one or more othermemory cells.

In some embodiments, coupling the data line with the power supply nodeincludes coupling write line WLB or WLT with power supply node VDD usingpre-charge circuit 124, each discussed above with respect to FIG. 1 .

In some embodiments, coupling the data line with the power supply nodeincludes using a switching device. In some embodiments, coupling thedata line with the power supply node includes using one or both oftransistors P4 or P5 of pre-charging circuit 400, discussed above withrespect to FIG. 4 .

At operation 620, in some embodiments, the data line is decoupled fromthe power supply node using the pre-charging circuit. Decoupling thedata line from the power supply node is performed by reversing operation610 for each of the embodiments discussed above, and includes thepre-charging circuit having a high output impedance with reference tothe data line.

The pre-charging circuit decouples the data line from the power supplynode in response to one or more logical states of the one or morecontrol signals being different from the one or more logical states thatcause the pre-charging circuit to couple the data line with the powersupply node. In some embodiments, the one or more control signals changelogical states in response to the start of a write operation on the oneor more memory cells associated with the pre-charging circuit. In someembodiments, the write operation includes writing data bits to each ofone or more memory cells and masking the writing of data bits to each ofone or more other memory cells.

Decoupling the data line from the power supply node is performed so thatthe data line is decoupled from the power supply node using thepre-charging circuit concurrently with operations 630, 640, and in someembodiments 660, each discussed below.

At operation 630, a first data signal is received at a first input nodeof a driving circuit coupled with the data line, the power supply node,and a reference node, and a second data signal is received at a secondinput node of the driving circuit. The first and second data signals aregenerated by the memory circuit and have logical states corresponding toa write operation in which writing a data bit to a memory cellassociated with the driving circuit is masked.

In various embodiments, in the masked write operation, the memorycircuit generates the first and second data signals each having thelogically low state, each having the logically high state, the firstdata signal having the logically low state and the second data signalhaving the logically high state, or the first data signal having thelogically high state and the second data signal having the logically lowstate.

In some embodiments, receiving the first and second data signalsincludes receiving the first and second data signals at respective inputnodes D1 and D2 of write line circuit 120B or 120T, discussed above withrespect to memory circuit 100 and FIG. 1 .

In some embodiments, receiving the first and second data signalsincludes receiving the first data signal with write driver 210 and thesecond data signal with interrupt circuit 220, discussed above withrespect to driving circuit 200 and FIG. 2 . In some embodiments,receiving the first and second data signals includes receiving the firstdata signal with write driver 210 and NOR gate NOR1, and receiving thesecond data signal with NOR gate NOR1, discussed above with respect todriving circuit 300 and FIG. 3 .

At operation 640, in response to the first data signal and the seconddata signal, the driving circuit is used to decouple the data line fromthe power supply node and the reference node. Decoupling the data linefrom the power supply node and the reference node includes the drivingcircuit having a high output impedance with reference to the data line.

The driving circuit decouples the data line from the power supply nodeand the reference node in response to the first and second data signalshaving the logical states corresponding to the write operation in whichwriting the data bit to the memory cell associated with the drivingcircuit is masked.

In some embodiments, decoupling the data line from the power supply nodeand the reference node includes using write line circuit 120B or 120T todecouple write line WLB or WLT from power supply node VDD and referencenode VSS, discussed above with respect to memory circuit 100 and FIG. 1.

In some embodiments, using the driving circuit to decouple the data linefrom the power supply node includes decoupling the data line from thepower supply node in response to the second data signal. In someembodiments, using the driving circuit to decouple the data line fromthe power supply node includes decoupling write driver 210 from powersupply node VDD using interrupt circuit 220, discussed above withrespect to driving circuit 200 and FIG. 2 .

In some embodiments, using the driving circuit to decouple the data linefrom the reference node includes the driving circuit responding to thefirst data signal. In some embodiments, using the driving circuit todecouple the data line from the reference node includes turning offtransistor N1 in response to the first data signal received at inputnode D1, discussed above with respect to driving circuits 200 and 300and FIGS. 1 and 2 .

In some embodiments, using the driving circuit to decouple the data linefrom the power supply node includes decoupling the data line from thepower supply node in response to the first and second data signals. Insome embodiments, using the driving circuit to decouple the data linefrom the power supply node includes decoupling output node OUT fromwrite driver 210 using NOR gate NOR1 and transistor P3, discussed abovewith respect to driving circuit 300 and FIG. 3 .

At operation 650, in some embodiments, operation 610 is repeated, andthe data line is coupled with the power supply node using thepre-charging circuit.

At operation 660, in some embodiments, the driving circuit is used tooutput a write line signal having one of a power supply voltage level ora reference voltage level on the data line. Outputting the write linesignal having the power supply voltage level includes outputting thepower supply voltage level carried on the power supply node, andoutputting the write line signal having the reference voltage levelincludes outputting the reference voltage level carried on the referencenode.

Outputting the write line signal having one of the power supply voltagelevel or the reference voltage level on the data line is in response tothe first and second data signals having logical states corresponding toa write operation in which writing a data bit to the memory cellassociated with the driving circuit is not masked.

In various embodiments, in the non-masked write operation, the memorycircuit generates the first and second data signals each having thelogically low state, each having the logically high state, the firstdata signal having the logically low state and the second data signalhaving the logically high state, or the first data signal having thelogically high state and the second data signal having the logically lowstate.

In various embodiments, outputting one of the power supply voltage levelor the reference voltage level on the data line is performed afteroperation 650 and/or before operation 610.

By executing some or all of the operations of method 600, a data line iscaused to float during a masked write operation, thereby obtaining thebenefits discussed above with respect to memory circuit 100 and FIG. 1 .

In some embodiments, a write line circuit includes a power supply nodeconfigured to carry a power supply voltage level, a reference nodeconfigured to carry a reference voltage level, an output node, first andsecond switching devices coupled in series between the output node andthe power supply node, and a third switching device directly coupled toeach of the output node and the reference node. The first switchingdevice is configured to selectively couple the output node to the secondswitching device responsive to a first data signal, the second switchingdevice is configured to selectively couple the first switching device tothe power supply node responsive to a second data signal, and the thirdswitching device is configured to selectively couple the output node tothe reference node responsive to the first data signal. In someembodiments, each of the first and second switching devices includes aPMOS transistor, and the third switching device includes an NMOStransistor. In some embodiments, the write line circuit includes aninverter including an output terminal coupled to a gate of the firsttransistor, and the inverter is configured to receive the second datasignal. In some embodiments, each of the second and third transistorsincludes a gate configured to receive the first data signal. In someembodiments, the write line circuit includes a pre-charge circuitincluding a first PMOS transistor configured to receive a first controlsignal and a second PMOS transistor configured to receive a secondcontrol signal, and the first and second PMOS transistors are coupled inseries between the output node and the power supply node. In someembodiments, the output node is coupled to a write line of a memorycircuit.

In some embodiments, a memory circuit includes first and second writelines coupled to first and second memory segments, and first and secondwrite line circuits coupled to the respective first and second writelines, each of the first and second write line circuits including apower supply node configured to carry a power supply voltage level, areference node configured to carry a reference voltage level, first andsecond PMOS transistors coupled in series between the power supply nodeand the corresponding first or second write line, and an NMOS transistorcoupled between the reference node and the corresponding first or secondwrite line. The first and second PMOS transistors of each write linecircuit are configured to selectively couple the corresponding first orsecond write line to the power supply node responsive to first andsecond data signals, the NMOS transistor of the first write line circuitis configured to selectively couple the first write line to thereference node responsive to the first data signal, and the NMOStransistor of the second write line circuit is configured to selectivelycouple the second write line to the reference node responsive to thesecond data signal. In some embodiments, the NMOS transistor of thefirst write line circuit is directly coupled to each of the first writeline and the reference node, and the NMOS transistor of the second writeline circuit is directly coupled to each of the second write line andthe reference node. In some embodiments, a gate of the first PMOStransistor and a gate of the NMOS transistor of the first write linecircuit are coupled to each other and configured to receive the firstdata signal, and a gate of the first PMOS transistor and a gate of theNMOS transistor of the second write line circuit are coupled to eachother and configured to receive the second data signal. In someembodiments, the second PMOS transistor of each write line circuit iscoupled between the power supply node and the first PMOS transistor ofthe corresponding write line circuit, the first write line circuitincludes an inverter configured to receive the second data signal andcomprising an output terminal coupled to a gate of the first PMOStransistor of the first write line circuit, and the second write linecircuit includes an inverter configured to receive the first data signaland comprising an output terminal coupled to a gate of the first PMOStransistor of the second write line circuit. In some embodiments, thesecond PMOS transistor of the first write line circuit is coupledbetween the first write line and the first PMOS transistor of the firstwrite line circuit, the second PMOS transistor of the second write linecircuit is coupled between the second write line and the first PMOStransistor of the second write line circuit, and each of the first andsecond write line circuits includes a logic gate configured to controlthe corresponding second PMOS transistor responsive to the first andsecond data signals. In some embodiments, each write line circuitincludes third and fourth PMOS transistors coupled in series between thepower supply node and the corresponding first or second write line, thethird PMOS transistor of each write line circuit is configured toreceive a first pre-charge enable signal, and the fourth PMOS transistorof each write line circuit is configured to receive a second pre-chargeenable signal. In some embodiments, the first memory segment includes abit line pre-charger configured to receive the first pre-charge enablesignal, and the second memory segment includes a bit line pre-chargerconfigured to receive the second pre-charge enable signal. In someembodiments, each of the first and second memory segments includes aplurality of SRAM cells.

In some embodiments, a method of floating write lines includes receivingfirst and second data signals at each of a first driving circuit coupledto a first write line and a second driving circuit coupled to a secondwrite line, wherein receiving the first and second data signals at thefirst driving circuit includes receiving the first data signal at afirst NMOS transistor coupled between the first write line and areference node configured to carry a reference voltage level, andreceiving the first and second data signals at the second drivingcircuit includes receiving the second data signal at a second NMOStransistor coupled between the second write line and the reference nodeThe method includes, in response to each of the first and second datasignals having a low logical state, using series coupled first andsecond PMOS transistors of each of the first and second driving circuitsto decouple the corresponding first or second write line from a powersupply node configured to carry a power supply voltage level, using thefirst NMOS transistor to decouple the first write line from thereference node, and using the second NMOS transistor to decouple thefirst write line from the reference node. In some embodiments, using theseries coupled first and second PMOS transistors of the first drivingcircuit to decouple the first write line from the power supply nodeincludes inverting the second data signal, and using the series coupledfirst and second PMOS transistors of the second driving circuit todecouple the second write line from the power supply node includesinverting the first data signal. In some embodiments, using the seriescoupled first and second PMOS transistors of the first driving circuitto decouple the first write line from the power supply node includesusing the first and second PMOS transistors coupled between the firstNMOS transistor and the power supply node, and using the series coupledfirst and second PMOS transistors of the second driving circuit todecouple the second write line from the power supply node includes usingthe first and second PMOS transistors coupled between the second NMOStransistor and the power supply node. In some embodiments, using theseries coupled first and second PMOS transistors of the first drivingcircuit to decouple the first write line from the power supply nodeincludes using the first PMOS transistor coupled between the first NMOStransistor and the power supply node and the second PMOS transistorcoupled between the first NMOS transistor and the first write line, andusing the series coupled first and second PMOS transistors of the seconddriving circuit to decouple the second write line from the power supplynode includes using the first PMOS transistor coupled between the secondNMOS transistor and the power supply node and the second PMOS transistorcoupled between the second NMOS transistor and the second write line. Insome embodiments, the method includes using series coupled third andfourth PMOS transistors of each of the first and second driving circuitsto decouple the corresponding first or second write line from the powersupply node concurrently with the using the series coupled first andsecond PMOS transistors of each of the first and second driving circuitsto decouple the corresponding first or second write line from the powersupply node during a write operation, and using the series coupled thirdand fourth PMOS transistors of each of the first and second drivingcircuits to couple the corresponding first or second write line to thepower supply node before and after the write operation. In someembodiments, using the series coupled third and fourth PMOS transistorsof each of the first and second driving circuits to decouple thecorresponding first or second write line from the power supply nodeincludes using the third PMOS transistor to decouple the correspondingfirst or second write line from the power supply node in response to apre-charge enable signal of a first memory segment coupled to the firstand second write lines, or using the fourth PMOS transistor to decouplethe corresponding first or second write line from the power supply nodein response to a pre-charge enable signal of a second memory segmentcoupled to the first and second write lines.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A write line circuit comprising: a power supplynode configured to carry a power supply voltage level; a reference nodeconfigured to carry a reference voltage level; a write line coupled to aplurality of bit lines of a memory array through a selection circuit; anoutput node coupled to the write line; first and second switchingdevices coupled in series between the output node and the power supplynode, wherein a source of the first switching device is directly coupledexclusively to a drain of the second switching device; an invertercomprising an output terminal coupled to a gate of the second switchingdevice; and a third switching device directly coupled to each of theoutput node and the reference node, wherein the first switching deviceis configured to selectively couple the output node to the secondswitching device responsive to a first data signal, the second switchingdevice and the inverter are configured to selectively couple the firstswitching device to the power supply node responsive to a second datasignal, and the third switching device is configured to selectivelycouple the output node to the reference node responsive to the firstdata signal.
 2. The write line circuit of claim 1, wherein each of thefirst and second switching devices comprises a PMOS transistor, and thethird switching device comprises an NMOS transistor.
 3. The write linecircuit of claim 2, wherein the inverter is configured to receive thesecond data signal.
 4. The write line circuit of claim 2, wherein eachof the PMOS transistor of the first switching device and the NMOStransistor of the third switching device comprises a gate configured toreceive the first data signal.
 5. The write line circuit of claim 1,further comprising a pre-charge circuit comprising: a first PMOStransistor configured to receive a first control signal; and a secondPMOS transistor configured to receive a second control signal, whereinthe first and second PMOS transistors are coupled in series between theoutput node and the power supply node.
 6. The write line circuit ofclaim 1, wherein the output node is coupled to a write line of a memorycircuit.
 7. A memory circuit comprising: first and second write linescoupled to first and second memory segments; and first and second writeline circuits coupled to the respective first and second write lines,each of the first and second write line circuits comprising: a powersupply node configured to carry a power supply voltage level; areference node configured to carry a reference voltage level; first andsecond PMOS transistors coupled in series between the power supply nodeand the corresponding first or second write line; and an NMOS transistorcoupled between the reference node and the corresponding first or secondwrite line, wherein: the first and second PMOS transistors of each writeline circuit are configured to selectively couple the correspondingfirst or second write line to the power supply node responsive to firstand second data signals, the NMOS transistor of the first write linecircuit is configured to selectively couple the first write line to thereference node responsive to the first data signal, and the NMOStransistor of the second write line circuit is configured to selectivelycouple the second write line to the reference node responsive to thesecond data signal.
 8. The memory circuit of claim 7, wherein the NMOStransistor of the first write line circuit is directly coupled to eachof the first write line and the reference node, and the NMOS transistorof the second write line circuit is directly coupled to each of thesecond write line and the reference node.
 9. The memory circuit of claim7, wherein a gate of the first PMOS transistor and a gate of the NMOStransistor of the first write line circuit are coupled to each other andconfigured to receive the first data signal, and a gate of the firstPMOS transistor and a gate of the NMOS transistor of the second writeline circuit are coupled to each other and configured to receive thesecond data signal.
 10. The memory circuit of claim 9, wherein thesecond PMOS transistor of each write line circuit is coupled between thepower supply node and the first PMOS transistor of the correspondingwrite line circuit, the first write line circuit comprises an inverterconfigured to receive the second data signal and comprising an outputterminal coupled to a gate of the second PMOS transistor of the firstwrite line circuit, and the second write line circuit comprises aninverter configured to receive the first data signal and comprising anoutput terminal coupled to a gate of the second PMOS transistor of thesecond write line circuit.
 11. The memory circuit of claim 9, whereinthe second PMOS transistor of the first write line circuit is coupledbetween the first write line and the first PMOS transistor of the firstwrite line circuit, the second PMOS transistor of the second write linecircuit is coupled between the second write line and the first PMOStransistor of the second write line circuit, and each of the first andsecond write line circuits comprises a logic gate configured to controlthe corresponding second PMOS transistor responsive to the first andsecond data signals.
 12. The memory circuit of claim 7, wherein eachwrite line circuit further comprises third and fourth PMOS transistorscoupled in series between the power supply node and the correspondingfirst or second write line, the third PMOS transistor of each write linecircuit is configured to receive a first pre-charge enable signal, andthe fourth PMOS transistor of each write line circuit is configured toreceive a second pre-charge enable signal.
 13. The memory circuit ofclaim 12, wherein the first memory segment comprises a bit linepre-charger configured to receive the first pre-charge enable signal,and the second memory segment comprises a bit line pre-chargerconfigured to receive the second pre-charge enable signal.
 14. Thememory circuit of claim 7, wherein each of the first and second memorysegments comprises a plurality of static random-access memory (SRAM)cells.
 15. A method of floating write lines, the method comprising:receiving first and second data signals at each of a first drivingcircuit coupled to a first write line and a second driving circuitcoupled to a second write line, wherein the receiving the first andsecond data signals at the first driving circuit comprises receiving thefirst data signal at a first NMOS transistor coupled between the firstwrite line and a reference node configured to carry a reference voltagelevel, and the receiving the first and second data signals at the seconddriving circuit comprises receiving the second data signal at a secondNMOS transistor coupled between the second write line and the referencenode; and in response to each of the first and second data signalshaving a low logical state: using series coupled first and second PMOStransistors of each of the first and second driving circuits to decouplethe corresponding first or second write line from a power supply nodeconfigured to carry a power supply voltage level; using the first NMOStransistor to decouple the first write line from the reference node; andusing the second NMOS transistor to decouple the first write line fromthe reference node.
 16. The method of claim 15, wherein the using theseries coupled first and second PMOS transistors of the first drivingcircuit to decouple the first write line from the power supply nodecomprises inverting the second data signal, and the using the seriescoupled first and second PMOS transistors of the second driving circuitto decouple the second write line from the power supply node comprisesinverting the first data signal.
 17. The method of claim 15, wherein theusing the series coupled first and second PMOS transistors of the firstdriving circuit to decouple the first write line from the power supplynode comprises using the first and second PMOS transistors coupledbetween the first NMOS transistor and the power supply node, and theusing the series coupled first and second PMOS transistors of the seconddriving circuit to decouple the second write line from the power supplynode comprises using the first and second PMOS transistors coupledbetween the second NMOS transistor and the power supply node.
 18. Themethod of claim 15, wherein the using the series coupled first andsecond PMOS transistors of the first driving circuit to decouple thefirst write line from the power supply node comprises using the firstPMOS transistor coupled between the first NMOS transistor and the powersupply node and the second PMOS transistor coupled between the firstNMOS transistor and the first write line, and the using the seriescoupled first and second PMOS transistors of the second driving circuitto decouple the second write line from the power supply node comprisesusing the first PMOS transistor coupled between the second NMOStransistor and the power supply node and the second PMOS transistorcoupled between the second NMOS transistor and the second write line.19. The method of claim 15, further comprising: using series coupledthird and fourth PMOS transistors of each of the first and seconddriving circuits to decouple the corresponding first or second writeline from the power supply node concurrently with the using the seriescoupled first and second PMOS transistors of each of the first andsecond driving circuits to decouple the corresponding first or secondwrite line from the power supply node during a write operation; andusing the series coupled third and fourth PMOS transistors of each ofthe first and second driving circuits to couple the corresponding firstor second write line to the power supply node before and after the writeoperation.
 20. The method of claim 19, wherein the using the seriescoupled third and fourth PMOS transistors of each of the first andsecond driving circuits to decouple the corresponding first or secondwrite line from the power supply node comprises: using the third PMOStransistor to decouple the corresponding first or second write line fromthe power supply node in response to a pre-charge enable signal of afirst memory segment coupled to the first and second write lines; orusing the fourth PMOS transistor to decouple the corresponding first orsecond write line from the power supply node in response to a pre-chargeenable signal of a second memory segment coupled to the first and secondwrite lines.